1. Field of the Invention
The present invention is directed to a sweep or read device for a storage luminescent screen in which x-ray images are latently stored, and in particular to such a device having a stimulating radiation source which generates a scan beam of stimulating radiation which causes the storage screen to luminesce, and a light conductor which conducts the emitted radiation to a radiation detector to convert the emitted light into an electrical signal sequence.
2. Description of the Prior Art
A sweep device having a drum in which the storage screen is mounted, a rotating deflecting mirror disposed in the center of the drum which directs the radiation from the stimulating radiation source onto the storage screen and a light conductor disposed for conducting the emitted light from the storage screen to a detector is described in European Application No. EP-A-0 179 247, corresponding to U.S. Pat. No. 4,692,813. This device undertakes a pixel-by-pixel scanning of the storage screen. A circular light-conducting plate of silica glass is connected to the detector, with the deflecting mirror disposed in the center of the plate. The plate conducts the light emitted by the luminescing storage screen to the light-sensitive entry face of the detector. For line-by-line scanning of the storage screen, the drum is shifted relative to the scanning and signal acquisition system, so that the rotating scan beam scans the screen line-by-line. Optimum light guidance is not, however, achieved using the circular light-conducting plate because a substantial portion of the light emitted by the storage screen is lost due to absorption or during the conductance of the light through the plate.
To avoid this problem, in several embodiments of the aforementioned European application and United States patent, the light conductor is disposed outside of a transparent drum. The simulating radiation is directed by the deflecting mirror through the transparent drum and onto the storage screen, with the resulting emitted radiation being guided to the detector via mirror faces of the light conductor. A problem with this solution, however, is that relatively large detectors must be used. It is possible to use light conductor having a plurality of mirror faces, so that multiple deflection within the conductor ensues, thereby permitting the use of smaller detectors. Such multiple deflection light conductors are, however, relatively difficult to manufacture. Moreover, because the detector must be arranged outside of the drum, the light conductor must exhibit a length which corresponds to the length of the storage screen to be swept. Light losses due to absorption are therefore increased.